In the first paragraph of the article appeas the following:
"One historian said that it [the razing of the city of Jerusalem] led to 'a catastrophe, indeed the ultimate catastrophe.'"
Who is the historian, and where did he say that?
A search using Google Books found the answers.
Israel in exile: the history and literature of the sixth century B.C.E.
By Rainer Albertz
On page 8 appears the source of the quote:
"Unlike the book of Jeremiah, the books of Kings assess the exile absolutely negatively. It is simply a catastrophe, indeed the ultimate catastrophe-or, put theologically, the judgement of Yahweh upon his disobedient people."
Actually, it is not the historian saying that the destruction of Jerusalem led to the "ultimate catastrophe", but rather the historian saying that the books of Kings say that it did so.
This book also gives 587/586 B.C.E. as to when the destruction of Jerusalem and the final elimination of Judah as a state took place.
No wonder that the Watchtower writer did not give a reference to this book!